Solid state of not, there smart meter still has to control it. A solid state relay for the compressor would be quite beefy/expensive. And a smart thermostat would not know that the compressor is not running due to “outside control”, and could throw up a fault light. My main point is it has to be additional wiring from the smart meter to the AC system.
—” A solid state relay for the compressor would be quite beefy/expensive. “
True, but not needed.
A Basic AC condenser has ground, L1 & L2 power, 24 vac (cooling) and neutral lines.
NOTHING MORE.
A woodpecker can peck a hole in your condenser coil and your blower will keep spinning...
The 24vac controls the contactor at the condenser and does the heavy lifting.